SAN DIEGO -- A man who swung his live-in girlfriend's 20-month-old son into a dresser in a drunken rage and pummeled a relative who tried to stop him pleaded guilty Friday to felony child abuse and assault with force likely to cause great bodily injury.

Cory Devon Demery, 20, will be sentenced to three years in prison at a Sept. 20 hearing, said Deputy District Attorney Teresa Santana.

Misdemeanor charges of resisting arrest and hitting an officer who responded to the scene were dismissed, the prosecutor said.

Police received an emergency call about the domestic disturbance in the 4200 block of 36th Street about 9:45 p.m. on Aug. 5.

Demery's 24-year-old girlfriend told officers the defendant had picked up her son by the ankles and swung him into a chest of drawers.

When her 40-year-old brother intervened, Demery attacked him, then chased him out of the apartment and continued beating him up across the street, according to police.

The older man eventually fled back into the couple's residence and locked himself inside, along with his sister and nephew. Demery then broke out a window, cutting his hands in the process, according to police.

When officers arrived, the defendant was initially cooperative, but became combative when they took him into custody.

Police said the toddler was treated for minor injures at Rady Children's Hospital and the woman's brother was taken to an emergency room, where he received 17 stitches for facial lacerations, police said.

Demery reportedly had been drinking heavily for several days, but it was unclear if anything other than intoxication motivated the rampage, according to police.

The suspect is not the father of his girlfriend's toddler son who was injured, Santana said.